Interpretive Summary: The desire for safe and more effective agrochemicals with reduced environmental and/or mammalian toxicity remains important. Essential to these efforts is the identification of new promising compounds possessing high levels of desirable biological activities and reduced harm to the environment. As part of our current research program, screening of plants native to the Republic of Kazakhstan for the presence of antifungal and antialgal constituents lead us to an investigation of Haplophyllum sieversii. Antifungal and antialgal natural compounds have been isolated from H. sieversii and tested for their ability to inhibit these organisms.

Technical Abstract:
Bioassay-guided fractionation of the hexane:ethyl acetate:water (H:EtOAc:H2O) crude extract of the aerial parts of Haplophyllum sieversii was performed due to preliminary screening data that indicated the presence of growth inhibitory components against Colletotrichum fragariae, Colletotrichum gloeosporioides, Colletotrichum acutatum. Fractionation was directed using bioautographical methods resulting in the isolation of the bioactive alkaloids flindersine, anhydroevoxine, haplamine, and a lignan eudesmin. These four compounds were evaluated for activity against C. fragariae, C. gloeosporioides, C. acutatum, Botrytis cinerea, Fusarium oxysporum, and Phomopsis obscurans in a dose-response growth-inhibitory bioassay at 50.0, 100.0, and 150.0 uM. Of the four compounds tested, flindersine demonstrated the highest level of antifungal activity. Additionally, flindersine, eudesmin, and haplamine were screened against the freshwater phytoplanktons Oscillatoria perornata, Oscillatoria agardhii, Selenastrum capricornutum, and Pseudanabaena sp. (strain LW397). Haplamine demonstrated selective inhibition against the odor-producing cyanobacterium O. perornata compared to activity against the green alga S. capricornutum, with lowest-observed-effect concentration values of 1.0 uM and 10.0 uM, respectively.